(Ch 5 & 6) linkage + Chromosome variation Flashcards
Genetic map
Genetic maps are base on recombinant frequencies RF and are created using mapping crosses
Linkage rule:
For any pair of linked genes, PARENTAL gametes are ALWAYS more numerous than recombinant gametes
For any pair of linked genes, PARENTAL gametes are ALWAYS
MORE numerous than recombinant gametes
Rule in genetic mapping cross about parents
One parent is heterozygous for all loci under consideration.
The other parent is completely recessive
Rule in genetic mapping cross about genotype of offspring
Phenotype of the offspring must reflect its genotype.
Fragile sites leads to ________
Deletions
Compensation loops allows ________
Present in what type of variations that would Make viable embryos: 1) & 2)
synapsis during meiosis –> allows meiosis to proceed
1) Duplications
2) Delitions
Tandem duplication
duplication of genes within the same region to give rise to the subsequent genes.
Unequal crossing-over may be the cause of _____________
some deletions / duplications
Effect of duplications
For some genes, having an extra copy may not cause any detectable problem. For others though, it can upset the carefully regulated interactions inside the cell, and create a problem.
Inversion heterozygotes
1) Definition:
2) Compensation
3) Trouble
1) Is when one chromosome is normal and the homologue contains an inversion.
2) Then inversion loops form when the two chromosomes synapse. (Compensation loops)
3) Trouble occurs when a crossover occurs within the inversion loop region
Segmental duplications are likely responsible for the existence of ________
Gene families: groups of genes with similar sequences whose products perform related (but not identical) functions.
Gene families
groups of genes with similar sequences whose products perform related (but not identical) functions.
Inversion heterozygotes lead to _______ _________
Reduced fertility
Fragile- X syndrome:
1) Repeat number increases when passed through ___________ _____________
2) Female penetrance _______ Male penetrance _______
CGG repeats near to the gene FMR-1 (fragile-X mental retardation)
1) Female germ-line
2) 30% 80%
Euploidy
Eu “true” ploidy “set.
Having a complete balanced sets of chromosomes
Aneuploidy
Refers to the condition of gaining or losing a single chromosome, so that the chromosome sets are no longer balanced. Ex Nullisomy, monosomy, disomy.
1) Nullisomy
2) Monosomy
3) Disomy
4) Trisomy
5) Tetrasomy
1) no copies of a specific chromosome
2) 1 copy of A chromosome in gametes is Normal. Abnormal if it is a somatic cell
3) 2 copies of A chromosome in somatic cells is Normal. Abnormal if it is in gametes.
4) 3 copies of A Chromosomes as in Patau +13 and Edwards +18
5) 4 copies fo chromosomes
Nondisjunction
An error in which homologues or sister chromatids are not segregated correctly in anaphase I or II of meiosis.
Trisomy in humans
1) Down syndrome
2) Patau syndrome
3) Edwards Syndrome
1) 47, XY or XX, +21
2) 47, XY or XX, +13
3) 47, XY or XX, +18
Nondisjunction has the most effect in ___
Mitosis of the cells of the early embryo
Polyploidy
named base on the number of complete sets: monoploid, diploid, triploid, tetraploid, pentaploid, etc.
Common in plants; also seen in lizards, amphibians, and fish, but incompatible with life in humans.
Odd-ploidies
are sterile and rarely found in nature.
1) Autopolyploidy
2) Autopolyploidy can arise from _________
1) is the addition of one or more extra monoploid SETS of chromosomes, identical to the existing sets.
2) nondisjunction in mitosis or meiosis
How to create an amphidiploid (fertile hybrid)
Use colchicine to duplicate the new hybrid
1) Polyploidy:
2) Autopolyploid:
3) Allopolyploid:
1) Is the presence of extra chromosome sets
2) posses extra chromosome sets from the same species.
3) posses extra chromosome sets from two or more species.
